Female hormones may block pain

March 14, 2003

A woman's tolerance of pain may have to do more with the power of her reproductive hormones than with the strength of her muscles, according to a new study.

"Our studies have shown that, although pain is influenced by both genetics and brain chemistry, it is clear that gender and hormones also play a role in our individual response to pain," said Dr. Jon-Kar Zubieta, a neuroscientist at the University of Michigan. "When estrogen levels are high, the brain's natural pain chemicals--endorphins or enkephalins --are much more potent."

One of the reasons women can tolerate the pain of childbirth is that estrogen levels soar before they deliver. According to the new research, this hormone activity increases the number of receptor sites in the brain where such natural pain-relieving chemicals as endorphins can "dock."

The more "ports" available to receive the endorphins, Zubieta said, the greater the ability of the brain to control the pain response and, ultimately, limit the pain a woman feels.